1. Field of the Invention
The present invention relates to a tachogenerator for speed control of electric motors and in particular for brushless d.c. motors.
2. Background of the Invention Including Prior Art
A motor has been proposed in German Offenlegungsschrift DE-OS 2 730 142. The windings of the tacho winding are disposed here next to the stator winding in the flat air gap of the main magnet, and the current changes in the statorwinding induce therefor in the tachowinding voltages interfering with a precise working control. On the other hand would a disposition of the tacho generator at a different position of the motor increase its axial length considerably, especially when a magnetic shielding between the motor and the tachogenerator is provided.
Therefor, it is a purpose of the present invention to provide a motor of the kind initially cited, which with compact construction and especially short length in direction of its rotation axis provides a low interference tacho signal remaining the same or improving with increasing age of the motor, for example in order to improve in any case, but at least to keep the same the ganging flutter of a speed controlled direct drive motor for a record player.